Analysis of 3 different tear strength testing methods
At present, there are three main methods for testing the tear strength of fabrics, namely: trouser-shaped method, trapezoidal method and impact pendulum method. The testing instruments include fabric tearing tester, Fabric tearing performance tester, fabric tearing strength machine, etc. For the three different testing methods, what principles are they based on? How is the experiment procedure different?
Impact pendulum tearing principle:
The sample is fixed on the fixture, an incision is made on the sample, and the When the pendulum is at a high potential energy position and the movable clamp leaves the fixed clamp, the sample is torn along the incision direction, and the work done to tear a certain length of fabric is converted into tearing force.
Principle of trouser-shaped tearing method:
Clamp the two legs of the trouser-shaped sample so that the sample incision line is on There is a straight line between the upper and lower clamps. Start the instrument to apply tensile force in the direction of the incision, record the tearing strength until the tear reaches the specified length, and calculate the tearing strength based on the peak value on the curve drawn by the automatic plotting device or through an electronic device.
Trapezoid tearing principle:
Draw a trapezoid on the sample and clamp it with the clamps of the strength tester Two non-parallel sides of a trapezoid. Apply continuously increasing force to the sample to cause the tear to propagate along the width direction of the sample, and determine the average maximum tearing strength.
1. Pendulum method tearing strength test steps:
Press the pendulum stop button and release the pendulum. Holding the pendulum as it swings back so as not to disturb the position of the pointer, read the tearing strength in Newtons from the scale graduations of the measuring device or from the digital display. Depending on the type of instrument used, the reading may need to be converted to Newtons by multiplying by a factor specified by the manufacturer. The inspection results should fall within the range of 15% to 85% of the scale used, and the test should be repeated at least 5 times in each direction.
Watch to see whether the tearing proceeds in the direction of the force and whether the yarn is removed from the fabric Slip instead of tear. The test that meets the following conditions is a valid test: a. The spinning yarn does not slip from the fabric; b. The sample does not slip from the clamp; c. The tear is complete and the tear has been within a wide range of 15mm. The above requirements are not met The test results should be eliminated. If 3 or more of the 5 samples are deleted, this method is not applicable.
2. Tear strength test steps of trouser method:
Start the instrument and tear the sample continuously at a stretching rate of 100mm/min Break to the end mark of the specimen. Record the tearing strength. If you want to get the tearing trajectory of the sample, you can use a recording instrument or electronic recording device to record the tearing strength and tearing curve of each sample in each fabric direction. If the peak value is from a high-density fabric, the number should be taken manually. The ratio of the walking speed and the stretching speed of the recording paper should be set to 2:1. Check whether the tearing is in the direction of the applied force and whether there is any spinning. The yarn slips through the fabric instead of tearing. Tests that meet the following conditions are valid tests: a. The spinning yarn does not slip from the fabric; b. The sample does not slip from the clamp; c. The tear is complete and the tear is along the direction of force application.
Test results that do not meet the above conditions should be eliminated. If the test results of 3 or more samples out of 5 are rejected, it can be considered that this method is not applicable to the sample.
If there is an agreement to increase the number of specimens, it is best to double the number of specimens and also to agree on how the test results will be reported.
3. Trapezoidal method tearing strength test steps:
Set the distance between the two clamps to (25±1) mm and stretch The speed is 100mm/min, and the appropriate load range is selected so that the tearing strength falls between 10% and 90% of the full scale; install the sample and place it along the trapezoidalClamp the sample on two parallel sides so that the incision is in the middle of the two clamps, keep the short side of the trapezoid taut and the long side in a wrinkled state; start the instrument, and if possible, use an automatic recording instrument to record the tearing strength. If the tearing force is not along the incision line, it is not recorded.
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